🌿 Weed
ANX-WEED-0000258
Blackjack
Bidens pilosa
Blackjack (Bidens pilosa), an annual broadleaf weed of the Asteraceae family.
- Family
- Asteraceae
- Growth habit
- Broadleaf
- Life cycle
- Annual
- Invasive status
- Naturalized, extremely widespread
- Native region
- Tropical Americas, now pantropical, especially widespread across sub-Saharan Africa.
- Reproduction
- Seed - barbed achenes ('beggar-ticks') that hook onto fur, clothing, and animal coats for dispersal.
Environment
Habitat & Growing Conditions
- Habitat
- Cultivated fields, roadsides, waste ground - extremely common across the tropics and subtropics.
- Climate requirements
- Tropical to warm temperate; grows year-round where frost-free.
- Soil types
- Tolerates a wide range of soils, including poor and disturbed ground.
Impact
Crops Affected & Economic Impact
- Affected crops
- Maize, beans, vegetables, and most smallholder food crops across Africa
- Competition impact
- Fast-growing and highly competitive for light and nutrients; can also host crop pests and diseases as an alternate host.
- Economic impact
- One of the most ubiquitous weeds of smallholder agriculture in tropical Africa, Asia, and Latin America.
Management
Control Methods
- Control methods
- Regular weeding cycles timed to prevent seed-head formation before harvest and dispersal.
- Organic control
- Hand weeding before flowering; young leaves are edible and used as a leafy vegetable/traditional medicine in parts of Africa.
- Chemical control
- Post-emergent broadleaf herbicides in larger-scale systems; less commonly targeted chemically in smallholder plots.